2009

Clearing Keys from Previous Animation
If you have animated any members of the IK chain interactively, or run Apply
IK previously, the existing animation keys will affect the new IK solution.
Sometimes that is exactly what you want. You can use manual animation to
subtly nudge the IK solution toward a particular result. However, it is more
likely that you want to remove old keys in order to begin the IK calculations
with a clean slate.
The Clear Keys option in the Inverse Kinematics rollout controls whether or
not old move and rotate animation keys are removed.
Constraining the IK Solution to Specific Frames
You use the Start and End fields in the Inverse Kinematics rollout to set the
range of frames used to calculate the applied IK solution. Using these fields,
you can restrict IK solutions to specific frames and solve for different solutions
in different time segments.
You can set the Start and End fields to include frames outside of the active
time segment.
You can also constrain an IK solution to frames where a key exists for an end
effector. This is useful if you want to animate a hierarchy using end effectors
but do not want keys generated on every frame.
Turn on Apply Only To Keys to constrain the IK solution to frames with end
effector keys.
Watching Progress of the IK Solution
Normally, Apply IK calculates all frames before updating the viewports. To
watch the progress of Apply IK frame by frame, turn on Update Viewports on
the Inverse Kinematics rollout.
Updating the viewports greatly slows down the Apply IK process but it can
help you troubleshoot complex animations.
Inverse Kinematics (IK) | 3465